Hypothesis update

This addresses an issue that came up in Ruud's book on Wed April 10 (URL change). ALso in modelling meeting Thu April 11 (didn't see annotations cause there weren't any!).

Partially closes Issue #31 (closed) (@tomvanwoudenbe you can close it if you don't care about those features any more like staticman). Also partial close Issue #77 (closed) - waiting on GitLab part.

@tomvanwoudenbe check the changed file name and location to see if oyu agree. THen all we have to do is add this text as an annotation to the page once it's live:

This is an example Annotation. Note that annotations are publicly visible, but you must create an account and be logged in to reply or make your own. You can make highlights, but they are only visible to you, not everyone. You can also see all the Annotations on a website by opening the "Public" menu at the top of this dialog pane, selecting "Public" again in the drop-down, then "View group activity." Make sure you type in the URL to search (e.g., teachbooks.tudelft.nl/jupyter-book-manual).